1. Field of the Invention
This invention relates to a steering column system for a motor vehicle.
2. Disclosure Information
Protection of the driver of a motor vehicle in the event of a frontal impact usually includes consideration of the driver's interaction with the steering column system. In a typical frontal collision the initial impact upon the front of the vehicle will be followed by an impact by the driver upon the steering column system. Automotive designers have attempted to mitigate the effects of these secondary impacts by building energy absorbing capability into steering column systems. One aspect of this energy absorbing capability addresses the location of the driver vis-a-vis the steering wheel. More specifically, various designs have allowed the steering wheel and its supporting structure to telescope axially forward or to rotate downward or upward when impacted by the driver. Examples of passive systems for rotating the steering column and steering wheel in the event of a collision are disclosed in U.S. Pat. Nos. 3,923,319 and 4,022,495. These systems are passive because rotation of the steering column and steering wheel in a desired fashion does not occur until the driver strikes the steering wheel. This phenomenon may be undesirable inasmuch as the driver's body will be subjected to considerable force to achieve the desired rotation of the steering column assembly.
A form of active rotational or tiltable steering column is disclosed in U.S. Pat. No. 3,988,027, in which explosive bolts are used to attach the steering column mounting bracket in the vicinity of the vehicle's dash panel. This system suffers from the problems associated with the use of pyrotechnic devices inside passenger compartments such as potential misfires, unreliable operation of electronic systems, and hazards to vehicle recyclers.
Designers have paid particular attention to energy absorbing arrangements incorporated into mounting hardward for a steering column. Examples of energy absorbing mounting arrangements are disclosed in U.S. Pat. Nos. 4,022,495 and 4,241,937. Each suffers from the problems faced by other passive devices in which desired repositioning of the steering column in the event of a collision is accomplished at the expense of energy absorbed by the driver's body.
U.S. Pat. No. 3,934,896 discloses an active system for repositioning the steering column in the event of rearwardly directed deformation forces in the area of the vehicle's front axle. Because this system relies on the steering drive shaft as part of its operating linkage, it is not suitable for use with steering systems in which the intermediate shaft extending between the steering column and the steering gear does not lie in the same vertical plane with the steering column and the point at which the intermediate shaft is attached to the steering gear. The system disclosed in the U.S. Pat. No. 3,934,896 is relatively inefficient in any event because considerable axial deformation will be required to effect the desired change in steering column inclination and parts of the system would be quite large and bulky. The U.S. Pat. No. 3,934,896 discloses another embodiment in which a linkage attached forward of the front wheel of the vehicle and slightly above the centerline of the wheel is pushed rearward and up to cause the steering wheel to rotate to a more vertical position. This embodiment will require a comparatively bulky and heavy structure for its operation which will depend upon axial displacement of a relatively great magnitude because of the disclosed rotational relationship between the steering column and the linkage mechanism.
U.S. Pat. No. 4,365,825 discloses a steering wheel mounting system in which the steering column is displaceable to a protective position during a collision or sudden deceleration. This system requires a substantial linkage which is complicated, high in weight, and not suitable for light duty vehicles.
U.S. Pat. No. 4,400,990 discloses a steering column assembly including a passive system which simultaneously allows axial deformation and radial movement to the upper steering shaft in the event of a collision.
Finally, U.S. Pat. No. 4,241,937 discloses a steering column support including a cantilevered beam mounted on the hinge pillar of the chassis. This too, is a passive device which will change its position only when struck by the driver's body during a collision.
It is an object of the present invention to provide a steering column system for a motor vehicle which beneficially rotates the steering column downward in the event of a frontal collision accompanied by rearward displacement of the vehicle's dash panel.
It is another object of the present invention to provide a steering column system for a motor vehicle including an active rotation device for beneficially rotating the steering column downward in the event of a frontal collision.
It is a still further object of the present invention to provide a steering column system for a motor vehicle which, in the event of a collision, will cause the steering column mounting bracket to be rotated forward to a further extent than that extent to which the dash panel of the vehicle is displaced rearward relative to the steering column system.
It is yet another object of the invention to provide a steering column system characterized by the aforementioned repositioning capability during collisions, in a system which is compact and light in weight.